Central infusion of melanocortin agonist MTII in rats: assessment of c-Fos expression and taste aversion.
Like leptin (OB protein), central infusion of the nonspecific melanocortin agonist MTII reduces food intake for relatively long periods of time (i.e., 12 h; W. Fan, B. A. Boston, R. A. Kesterson, V. J. Hruby, and R. D. Cone, Nature; 385: 165-168, 1997). To test the hypothesis that MTII may influence ingestive behavior via mechanisms similar to those that mediate the effects of leptin, we infused a single dose of MTII into the third ventricle (i3vt) of Long-Evans rats and examined three dependent measures that have been studied following i3vt infusion of leptin: 1) effects on long-term food intake and body weight (48 h), 2) patterns of c-Fos expression in the brain, and 3) conditioned taste aversion learning. Similar to leptin, MTII reduced 48-h food intake (1.0 nmol dose), reduced body weight at 24 and 48 h (0.1 and 1.0 nmol doses, respectively), and induced c-Fos expression in the paraventricular nucleus of the hypothalamus and the central nucleus of the amygdala. In contrast to leptin, MTII was found to produce conditioned taste aversions. These results are consistent with the hypothesis that MTII may influence regulatory behavior via mechanisms similar to those that mediate the effects of leptin.
Thiele
T E
TE
Department of Psychology, University of Washington, Seattle 98195, USA.
van Dijk
G
G
Yagaloff
K A
KA
Fisher
S L
SL
Schwartz
M
M
Burn
P
P
Seeley
R J
RJ
D000284:Administration, Oral; D000679:Amygdala / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology*; D005247:Feeding Behavior / Q000187:drug effects*; D007263:Infusions, Parenteral; D020738:Leptin; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000819:agonists*; D009765:Obesity; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*; D011506:Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D012439:Saccharin / Q000008:administration & dosage / Q000494:pharmacology; D013649:Taste; D000521:alpha-MSH / Q000031:analogs & derivatives* / Q000494:pharmacology
D020738:Leptin; D011506:Proteins; D016760:Proto-Oncogene Proteins c-fos; C081720:alpha-MSH (4-10)amide, Ac-Nle(4)-cyclo(Asp(5)-Phe(7)-Lys(10))-; D000521:alpha-MSH; D009074:Melanocyte-Stimulating Hormones; D012439:Saccharin